Safety pressure relief device support



April 18, 1961 R. s. COFFMAN 2,980,286

SAFETY PRESSURE RELIEF DEVICE SUPPORT Filed on. s, 1956 2 Sheets-Sheet 1 ROBERT S. COFFMAN INVENTOR.

ATTORNEY April 1961 R. s. COFFMAN 2,980,286

SAFETY PRESSURE RELIEF DEVICE SUPPORT Filed 001;. 8, 1956 2 Sheets-Sheet 2 ROBERT S. COFFMAN INVENTOR.

ATTORNEY United Stat SAFETY PRESSURE RELIEF DEVICE SUPPORT Robert S. Coiiman, Kansas City, Mo., assignor to Black, Sivalls & Bryson, Inc., Kansas City, Mo., a corporation of Delaware Filed Oct. 8, 1956, Ser. No. 614,610

7 Claims. (Cl. 220-89) The present invention relates generally to a safety pressure relief device and more specifically to a support for a dome-shaped rupturable disc-type safety pressure relief device.

A majority of the rupturable disc-type safety pressure relief devices presently being used are dome-shaped. If they are not pro-bulged prior to being put into service, they will assume a dome shape immediately upon being exposed to pressure.- Therefore, it has been found to be more expedient to pre-bulge the rupturable discs to a dome shape which has a higher crown height than the rupturable disc would have when exposed to service condition pressures. The advantage of this pre-bulging is that the crown height of the rupturable disc is then known for all normal service pressures and that this dome-shaped rupture disc may be provided with adequate support since its dome shape and crown height are known prior to installation.

Supports are needed under a dome-shaped rupture disc if it is ever to be subject to pressure differentials across the disc whereby the higher pressure is exerted on the convex side'of the disc. This condition often occurs in pressure systems that are subject to conditions of vacuum, that is, pressure less than atmospheric. Such supports are generally given the designation, vacuum supports. Vacuum supports should be designed with two basic requirements in mind. First, the supports should be sufliciently strong to protect the rupture disc at all possible vacuums which may occur. Second, the supports should be sufiiciently weak to completely open so that the relief area will not be obstructed by the support once the rupture disc has failed. Prior to the present invention, vacuum supports generally were domeshaped members positioned under dome-shaped rupture discs. Many of these previous designs have provided sufficient support under conditions of vacuum but have failed to open to clear the relief area when the rupture disc bursts. This failure to open may be due to excessive strength of the support device or it may in some types be caused by cohesion of the parts of the device due to corrosive conditions to which the support has been exposed. Some of the previous types of vacuum supports have been known'to fail to adequately open when the rupture disc fails and thus have obstructed the relieving of the pressure in the vessel or system being protected. Also, in the use of some of the previous types of vacuum supports, the vapors of the system being protected have been known to solidify in the space between the supports and the rupture disc. This can cause a gradual build-upof solids which may eventually cause a premature failure of the rupture disc.

Most previoustypes ofl vacuum supportsfor domex sha e'drupture members have been dome-shaped and positioned under the dome-shaped rupture member. This nd 't units, the vacuum support and the rupture disc, be made of a corrosion-resistant material. Another disadvantageous feature of previous vacuum support design is their complexity of design. Therefore, the primary object of the present invention is to provide a new and novel vacuum support for dome-shaped rupturable disctype safety pressure relief devices.

A further object of the present invention is to provide a vacuum support for a dome-shaped rupture disc which will be protected from.corrosive conditions by the rupture disc.

A still further object of the present invention is to provide a novel vacuum support for a dome-shaped rup ture disc which will be positioned on the convex side of the rupture disc.

Another object of the present invention is to provide a vacuum support for a dome-shaped rupture disc which may be positioned in such a manner that a deposit of solids between the support member and the disc is effectively prevented.

Still another object of the present invention is to provide a novel vacuum support for a dome-shaped rupture disc which will provide adequate support for the rupture disc under conditions of reversed pressure differential and which will open upon failure of the rupture disc to allow normal pressure relief of the system being protected.

In accomplishing these and other objects of the present invention, I have provided improved details of structure, the preferred form of which is illustrated in accompanying drawings wherein:

Fig. 1 is a sectional view of a safety pressure relief device including the novel vacuum support of the present invention.

Fig. 2 is a sectional view of another type of safety pressure relief device which also includes the novel vacuum support of the present invention.

Fig. 3 illustrates the component parts forming the rupture assembly illustrated in Fig. 1, such parts being shown in disassembled spaced relationship- Fig. 4 illustrates the component parts forming the rupture assemblyillustrated in Fig. 2, such parts also being shown in disassembled spaced relationship.

Referring more in detail to the drawings:

Safety pressure relief device 1 shown in Figs. 1 and 3 is composed of base flange 2, holddown flange 3, rupture assembly 4 positioned between flanges 2 and 3, studs 5 and nuts 6 on studs 5 securing flanges 2 and 3 together.

Rupture assembly 4 is composed of a lower sealing member 7, a slotted rupture member 8, support member 9 and an upper sealing member 10. It should be noted that the design of lower sealing member 7 and slotted rupture member 8 generally conforms to the specification of my co-pending application Serial No. 455,333, filed on September 10, 1954. 7

Upper and lower sealing members 10 and 7 are generally made of a resilient, corrosion-resistant material such as polyethylene. It has been found that relatively thin metal can be formed to function properly as a sealing member inrupture assembly 4, but in general the resilient plastic-type material has been found best suited N corivex disc and is spot welded at one side only, will fold-upwardly whenrupture member 8 rupturesto allow -a'complete opening of relief area 12, the area through fiange 3.; Support member 9 is formed to have a dished pawn" approximately the contour of rupture member 8;

"flanges 2 and; 3,

Sealing members .7 and .10 are either formed or positioned will not appreciably affect the rupture pressure of rupture member 8, In designingsuch units, it is desirable to take into consideration the strength added 'by members 7 and itl'when calculating'th'e rupture pressure of the complete rupture assembly 4. 7

Safety pressure relief device 13 shown in Figs. 2 and 4 illustrates the .use of the support of the present invention in combination withastandard dome-shaped rupture disc. Rupture assembly 14 is positioned between .base flange 15and holddown flange 16, the flanges 15 and 16 being secured together bystuds 17 and nuts 18.

.Rupture assembly '14 comprises a lower dome-shaped rupture disc 19, suppo'rtjmember and upper sealing member 21. Dome-shaped rupture disc 19 will normally rupture disc 19 in one position to allow opening of relief area 23 when rupture disc 19 fails. Also, rupture disc 19 and support 20 aresufiiciently' domed so that they will not have any additional growth in crown height under normal operating conditions. Supportmember 20 provides support for rupture disc 19 by transmittingany back pressures to its outer periphery and to the portion of rupture disc 19 which is contacted at the outer periphery of support member 20. Since the central portion of rupture disc 19 is the; weakestrportion, it is completely protected against vacuumsand back pressures. It is advisable to minimize the volume of air trapped between rupture disc 19 and upper sealing member 21 since, under conditions of vacuum within relief area 23, this trapped air will exertpressure on rupture disc 19 in such a manner that support 26 cannot provide support for rupturedisc 19.

be" of ametallic material such as aluminum'or steel to r V which support member 20 maybe spot welded as shown at 22 ,As'previously discussed support member 20 is secured by spot weldi'ngat only one place in order to allow a complete opening of the relief area 23 through holddown flange 16 when rupture disc 19 fails. Sealing member 21 will normally be made of a resilient material such as polyethylene but may be formed of other materials which will block the flow of external air into the space between rupture disc 19 and supportmember 20. Seal ing member 21, like sealing member 10, is comparatively into the pressure system which is to be. protected. 7 Once 7 installed, pressure is exerted through base flange 2 against 7 lower'sealing member This will cause member 7 to completely engage I and transmit the system press'ure 7 against slotted rnpturememberS, Since the crown height a of member ,8 is predetermined,-it will retain its height which may occur in the s'ystemwill be transmitted through upper sealing member 10 to support member 9. Sup- ]por't member 9, being of the sameicontou-r as slotted" rupture member 8, will transmit the reverse pressure to the outermost periphery of contact between support member 9 and slotted rupture member 8 therebytpreventing adjacent w h 7 but this deflection will not befsuflicient V the weakest point of rupture assembly 4 is the space'between .the ends ofthejslots in slotted rupture member 8.

bly A from any possible" corrosive conditions existing "in the'protected systemand also will protect agaiustplf im r tu're' failurel of rupture assembly 4 due tome deposit of solids on rupturem'ember' 4 from the protected system 7 l i1 f-Safety'pr'essure jrelief device :13 shown in Fig; "2 jfunctionsfsimila'rly, to safety pressure relief :device; 1 shown} in f-Ei'gfl exceptithatdome shaped mpture disc1f19:is. ro e J protected against vacuum nd back; pressures ratherthan 'lOttedf ture member Support 20, functions sn a rmah e s m it? nqtibnsfi c 'a t6 slotted rupture member 8.

Support 20,;iszweldedj 7 weak in strength so that it will not appreciably affect 30' the rupture pressure of iupture disc 19.

rln operation, safety pressure relief device 1 shown in Pig. "1 is installed into a system by welding orotherwise suitably connecting base flange 2 to a pipe connecting Therefore, from the foregoing it may readily be seen 7 vacuum support including, a rupture member having 'a central concave-convex portion, the concave side of said portion adapted to be exposed to pressures/two sealing membranes, said membranes positioned onboth sides of said rupture member and a concave-convex support member positioned in nesting relationship with the convex side of said rupture member. between said rupture member and one of said sealing members.

i '2 A safety pressure relief device comprising: a domeshaped imperforate rupture disc'adaptedto rupture at a predeterminedpressure, said rupture disc having its concave side normally exposed to "pressures-utobe relieved and positioned across a pressure relief passageway to contain pressure therein, a dome-shaped vacuum support member positioned and-closely fitting on the convex'surrupture member 8 from being reversely dishedandconse' r "quently weakened. This position of supportmember'9 above slotted rupture member 8 may cause :aslightflexj I ing of slotted rupture member 8 near its o'uter'periphery to the position where 'it' is 'clampe'drbetween 2 face of said rupture disc, and a sealingrnember positioned on: the convex side of said support member and providing a seal'between the edge of the latter and said rupture disc, said sealing memberbeing'weaker than the said rupture discpso as to have nofappreciable efiect on the rupture characteristics of said pressure reliefdevice.

, 3.:Invention' according to claim 2-wherein theouter diameter of said dome-shaped support member is smaller than the diameter of said" pressure relief passageway.

4, Safety pressure relief apparatuscomprising a dome- -shaped deviceadapted 'to rupture at a predetermined pressure and havinga peripheral clampinigtlan'gasaid device being adaptedtobe positioned across aipressure re- =liefpasageway with its concave side exposed to thepressure to be relieved; a dome-shapedvacuumsupportmemrber of'a diameter less than that of said rupture device 7 to cause a premature rupture ofruptureassembly 4 since I-IThus, support member 9. will provide adequatesup-j V t V r a H, i port for; slotted rupture'member s :andwill allow 11 Sald suppqrtimember'ppsmoneidjgamst' the convex Side use of -a sealing, membrane (lowerf sealing m'en'iber;- 7 lbelow'slotted rupture member Sto protect rupture assem-g.

of said apparatusi 7. t

and positioned against the convex side'of the-latteryand ase'aling membrane of a diameter greater thanthat-cf of the latter, whereby under vacuum gondition'sysubstantially only {the peripheral edge ofls'aidf portmember exerts a buckling forcer on saidirupturefdey ce, said, sealing membranef being weaker"than saidjdeyice solas" to" V e: rupturecharacte s'tics have y no .appreciable' effech V port member is secured at ,6. The structure 7 d fie m T's-V ture device comprisesg a'sin gle impe'rfor'a membrane positioned on the concave side of said slotted member.

References Cited in the file of this patent UNITED STATES PATENTS Raymond July 12, 1938 Simpson et a1 Sept. 19, 1950 

